The invention relates to a method for increasing the heat efficiency of a piston combustion engine by utilizing the heat generated in the course of the combustion process in an additional steam-gas cycle performed after the normal working cycle of the engine. Is is currently known that a substantial amount of heat generated in the course of the combustion process is dissipated together with exhaust gases and with the cooling water into the surrounding space without being transformed to mechanical energy.
The heat efficiency of piston combustion engines has been already tried to increase by different methods. One of said methods is described in the U.S. Pat. No. 1,794,799 of A. Schwartz, where a two-stroke cycle has been added to the existing two or four stroke working cycle of the engine, wherein water is injected into the cylinder during the second additional firing or power stroke. Due to an intensive cooling down of hot compressed combustion products a quick pressure reduction is experienced at the beginning of the following expansion stroke, so that the energy gained by this additional cycle mostly surpasses the energy required for additional compression.
Another known attempt of this kind has been described by Bruce Grover in Mechanical Engineering of December 1973, where again a couple of strokes have been added to the working cycle of the combustion engine and in the course of the additional fifth stroke water is injected into the cylinder, in a way similar to that of Schwartz. The amount of injected water is controlled by a thermostat.
Other methods for transformation of waste heat at combustion engines to mechanical energy have been also proposed, using complicated arrangements demanding on material and manufacturing costs and operating with substantial losses of energy. There is however no known method where the waste heat could be efficiently transformed directly to mechanical energy on the engine shaft without complicated additional means.